1. Field of the Invention
The present invention generally relates to improvements in electromagnetic release mechanisms for cameras and it relates more particularly to an improved camera release mechanism of the type having an electromagnetic device which includes a permanent magnet for retaining a release member in a cocked retracted or inoperative position against a biasing force, and an electromagnetic coil energizable for producing an electromagnetic force or field opposite to the magnetic force or field of the permanent magnet to release the release member and allow it to move to its operating position where it initiates a camera operation, such as the shutter opening or the retraction of a reflex mirror and/or the stopping down of a diaphragm prior to the shutter operation in a single lens reflex camera.
2. Description of Prior Art
In the conventional electromagnetic release mechanisms of the above type, the release member is always biased or urged by a spring towards its operating position, i.e. in a direction to move away from the electromagnetic device which normally retains the release member by the force of the permanent magnet. Thus the release member must be returned to its inoperative position by a force overcoming the force of the biasing spring. Thus, if it is contemplated in the conventional camera to return the release member automatically in relation to a camera operation, such as the termination of exposure, such camera requires the returning mechanism to have a great power to overcome the force of the biasing force, resulting in an increase in the power required for the camera cocking operation. This increase of power is unfavorable from the view point of a smooth camera operation. If a weaker spring is selected for the biasing of the release lever in order to lessen the power required for the camera cocking operation, then the operation of the release lever is unreliable and causes a delay in the initiation of the camera operation and may even possibly fail to actuate the camera.
Improved electromagnetic release mechanisms including an associated permanent magnet and electromagnetic coil, but free of the above drawbacks, have been proposed in pending U.S. Patent Application Ser. Nos. 805,954 and 821,109 now respectively, U.S. Pat. Nos. 4,133,609 and 4,132,474, issued respectively on Jan. 9, 1979 and Jan. 2, 1979 which are assigned to the same assignee as that of the present application.
In the proposed mechanisms, the release member is free from the force of a biasing spring during its return operation, with the biasing spring being charged with the camera cocking operation. Thus, less power is required for the return of the release member and also for the camera cocking operation.
The improved mechanism of the present invention broadly functions in a manner similar to the heretofore proposed mechanisms but with a simpler construction which is more practical and is suitable for mass production.